Various types of seals have been used to prevent leaking of fluid from actuator or metering cylinders in the area where a piston or piston rod passes through an opening in the end of the cylinder.
An example of cylinders needing such a seal may be found in U.S. Pat. No. 5,499,745 Darian et al, which was copending herewith. The cylinders in the above mentioned application are used for metering quantities of two different fluid materials such as a resin and a hardener to a mixing dispenser where the materials when mixed, become an epoxy adhesive. Various materials such as paint, gasket material and caulking materials can be mixed and dispensed from this type of equipment which is designed to assure that the proper quantities of each of the two materials is provided so that the mixture of the end product will function as intended.
When metering viscous materials through cylinders of the type described above one of the problems encountered is that either the material will start to cure up between the piston and the seal ring of the cylinder or solid particles will tend to separate from the liquid or oil type substance of the fluid material and will weep out past the seal ring and increase the friction in the area of the seal ring and may even cause the piston and piston rod to seize up. When the solid particles separate from the oil of the material the material is said to "pack out".
Some adhesive materials are anaerobic in nature. The packed out anaerobic materials in the seal area, being away from the air, will cure up in even less time than non anaerobic sealers.
To assure effective operation of the piston within the cylinder carrying this viscous type of material, it is important to prevent curing or packing out of the material in the area between the piston and the seal ring surrounding the piston.